1. Field of the Invention
The present invention relates to homogeneous, flexible block copolyetheramides prepared from (1) monomers which produce crystalline amide blocks (short-chain dicarboxylic acids and short-chain aliphatic diamines), (2) polymeric diacids or amino derivatives of polymeric diacids, and (3) polyoxyalkylenediamines or polyoxyalkylenedicarboxylic acids.
2. Description of the Prior Art
In certain plastics applications there is a need for polymers which have a set of chemical and physical properties which are partly characteristic of the polyamides. It may be necessary to add the requisite of flexibility to the chemical resistance and to the good heat behavior properties of the conventional polyamides obtained by polycondensation of short-chain saturated aliphatic dicarboxylic acids with short-chain saturated primary aliphatic diamines. Many copolymers have been suggested for this purpose, but the required combination of properties is rarely obtained.
U.S. Pat. No. 4,218,351 describes copolyetheramides containing crystalline amide blocks (capable of conferring the required good thermal behavior properties) produced from short-chain dicarboxylic acids and short-chain diamines, which are capable of having a good flexibility, especially at low temperature. These copolyetheramides are obtained by direct reaction (1) of a mixture of a short-chain dicarboxylic acid and a short-chain diamine with (2) a fatty acid dimer or an amino derivative of a fatty acid dimer and with (3) a polyoxyalkylenediamine or a polyoxyalkylenedicarboxylic acid. However, when following the teachings of this patent it was found that the copolymers thus obtained have the drawback of not being homogeneous, the detrimental consequences of which being on the one hand, the development of properties which do not attain the required high values which are compatible with the use of copolymers as technical plastics and, on the other hand, a great difficulty in providing for the production of highly reproducible shaped articles.